The present invention relates to a driving device for rolls in high speed rolling mills and the like.
A drive shaft for driving the working rolls of a rolling mill, for example, interconnects a drive shaft element and the neck portion of the working roll, which is a driven shaft element, and through universal joints included at two places in the drive shaft itself it also effects the centering of the drive and driven shaft elements and the transmission of torque. The fitting yoke and the coupling at the opposite ends of the drive shaft are fitted on the ends of the drive and driven shaft elements, whereby the drive shaft is connected to these shaft elements.
The serious drawback inherent in such conventional drive shaft lies in the fact that in order to facilitate the mounting and dismounting of rolls, the fit between the neck portion of the working roll, which is the driven shaft element, and the coupling is a clearance fit, the clearance resulting in a rotational vibration being exerted in the drive shaft, said rotational vibration being transmitted to the working roll and greately decreasing the accuracy of rolling while repeatedly imparting a vibratory impact to the bearings supporting the working roll and the backup roll and hence damaging these bearings in a short period of time.
On the other hand, recent rolling mills are confronted by the important problems of speeding up the rolling operation and improving the rolling accuracy and the rate of operation. With the conventional driving device, however, the adverse influence of said vibration becomes more conspicuous with the speedup of the rolling mill and there are difficulties in providing a sufficient mechanical strength. If the roll neck and the coupling are fitted together with an interference fit in order to eliminate said vibration, the exchange of rolls would become impossible. Thus, it has been impossible to solve said problems.
As measures to prevent such vibration due to clearance fit, the applicant has previously proposed constructions for fit between the coupling and the driven shaft element, as shown in FIGS. 1 and 2. According to these constructions, to provide for fitting between the coupling A of a drive shaft and a driven shaft element, such as the roll neck B of a working roll, a conical opening a or b' is provided either in the inner bottom surface of the coupling or in the end surface of the roll neck B at its center while a cone b or a' is provided on the other, and said conical opening and cone are fitted together, whereby the central axes of the coupling and working roll are correctly aligned with each other despite said clearance fit. In this case, however, the provision of a cone or a conical opening at the end surface of the roll neck of a working roll results in the center hole of the working roll, which has been provided at said end surface, being damaged, bringing about a drawback that it becomes difficult to determine the base axis in connection with regrinding or re-turning the working roll.